1. Field of the Invention
The present invention relates to apparatuses and processes for recording dye-based recordable DVD media, wherein the recording layers of the DVD media cause changes in optical properties such as transmittance and reflectance through irradiating optical or laser beams, thereby enabling recording and reproducing information.
2. Description of the Related Art
Recently, recordable digital versatile discs (DVD-R) have been developed for providing advanced large capacity optical discs. In order to enhance recording capacity of optical discs, recording materials have been improved to micronize recording pits, image compression formats such as MPEG2 have been developed, and semiconductor lasers have been improved to shorten the wavelength for reading recording pits.
Conventionally, as for recording and reproducing semiconductor lasers at red wavelength regions, only AlGaInP laser diodes have been commercially utilized at 670 nm, for example, for barcode readers or instrumentation units. Nowadays, red lasers are remarkably expanding their markets in terms of optical storage products along with optical discs being highly densified. DVD drives are standardized at two wavelengths of 635 nm and 650 nm using laser diodes, and DVD-ROM drives of wavelength 650 nm are commercially available.
Typically, in dye-based recordable DVD media where pits or marks are formed by use of heat mode, the pulse width and the recording power of laser pulse are optimized at a specific recording rate, thus there exist a problem that the marks and/or spaces are different at the other recording rates. Namely, dye-based recordable DVD media suffer from problems that mark widths are hardly uniform, mark lengths are often elongated or shortened, and jitter properties tend to degrade with time, since thermal capacity from heat pulses turns into insufficient that is required to form marks at edges, and the heating temperatures are different from the optimal decomposing temperature, therefore, the average length of marks tends to fluctuate and the duty ratio of optimal heating pulse comes to different.
In addition, as for physical formats of DVD media, the format of DVD-R media is standardized through partially cutting the land portions of so-called land pre-pits. According to the format, there are problems that pre-pit information such as pre-pit addresses cannot be properly reproduced when the land pre-pit signal is less than 0.16; on the other hand, the land-pit signals themselves act noisily when the land pre-pit signal is more than 0.32 at data region, thus resulting in frequent occurrences of data errors. Accordingly, in order to utilize land pre-pit signals, there arises a disadvantage that cut width should be adjusted with respect to the recording material by a stamper, which is a mold to transfer a signal recording portion of original pattern to resin substrates and is utilized at an injection molding cavity, and the land cut width should be adjusted so as to control the land pre-pit signal into the range of 0.16 to 0.32.
In the prior art concerning the recordable DVD media that employ a dye in the recording layer, Japanese Patent Application Laid-Open (JP-A) No. 2004-195764 discloses employment of polymethine dyes or combination of polymethine dyes and optical stabilizers as recording material; JP-A Nos. 09-309268 and 11-34499 disclose employment of a layer formed from tetraazaporphyrin (porphyrazin) dye or combination of cyanine dyes and azometalchelate dyes (salt forming dye) and a reflective layer as a recording layer;
JP-A No. 08-295079 discloses employment of formazane (metal chelate) dye and the other dyes as the recording material; and JP-A No. 10-162430 discloses employment of dipyromethene (metal chelate) dye and the other dyes as the recording material; and further, many proposals appear that perform multi-pulse recording by means of dyes as the recording materials. In addition, such recording is also demanded that performs one pulse recording on dye-based recordable DVD media while optimizing the recording waveform to perform recording at higher linear velocity.